DESCRIPTION (Taken from application) Currently, there is scientific and public concern about whether exposure to putative endocrine disruptors, such as polychlorinated biphenyls (PCBs), are associated with adverse reproductive health effects. This concern stems from studies showing that PCB residues are found in a large proportion in a large proportion of the general population, as well as animal and some human studies suggesting possible associations of exposure to PCBs with altered reproductive function. The proposed study will investigate the relationship between PCBs and endometriosis, which is an important public health issue because it affects more than five million women in the United States and has large social and economic impacts. Endometriosis is a relatively common disease (prevalence estimated at 5 to 10%) that can affect fertility as well as other aspects of a woman's general health and well-being. Animal and human data suggest that the critical exposure window for endocrine disruptors may be in utero because the developing fetus is extremely sensitive to endocrine hormones during reproductive development. Therefore, the proposed epidemiologic study is designed to investigate the relationship between in utero exposure, the hypothesized critical exposure window, and endometriosis and menstrual cycle dysfunction. The proposed project, a case-control study nested in the National Collaborative Perinatal Project (NCPP) cohort, will extend follow-up through the reproductive years of the daughters of the pregnant women recruited in the NCPP (1959-1966). During pregnancy, one or more blood samples were taken from the pregnant women and archived. The daughters will be traced and will complete a question on endometriosis and menstrual cycle characteristics. Cases are daughters with laparoscopy-confirmed endometriosis. The NCPP cohort provides a unique opportunity to study in utero exposure to PTCBs and female reproductive to PCBs and female reproductive health without having to initiate an expensive prospective study and follow individuals for 20 or more years. In addition, in the proposed, a current blood sample will be analyzed to reflect adult PCB levels that may confound the relationship between endometriosis and in utero PCB exposure, and will serve as a source of additional information on cumulative exposure. The area of human reproductive health effects of endocrine disrupting chemicals, such as PCBs, was identified as a current topic for special emphasis by the NIEHS.